In order to manufacture bags continuously from a plastics strip-shaped film, the strip-shaped film is generally folded double, successively heat-sealed and then out along predetermined lengths to manufacture the individual bags. In such a manufacturing process, it is advantageous if the film is formed into loops by bending it in a zig-zag shape at the time of feeding to control the dimensions of the film and minimize the size of the apparatus. In the particular art, a device is known in which a film is formed into loops using two sets of rotating drums. This device is equipped with a mechanism in which film supporting members are arranged on the surface of respective drums at a predetermined pitch, these supporting members being made to mesh with one another by the rotation of mutually opposing drums. However, with the arrangement employing the abovementioned rotating drums, there is a problem that the meshing condition of the supporting members is restricted by the rotating movement of the drums. For instance, the length of the loops decided by the meshing depth of the supporting members, and the amount of the meshing depends on the eccentricity among the rotating shafts.